Jefri Marzal and  Hong Xie and  Chun Che Fung,  Vertex Configurations and Their Relationship on Orthogonal Pseudo-Polyhedra.   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    May 2011, vol. 53(5). 415 - 422
    [viewed 19 January 2020]. Available from: https://publications.waset.org/pdf/14765.